1. Field of the Invention
The present invention relates to an anti-seizing agent. Particularly, the present invention relates to an anti-seizing agent for preventing seizing of parts that may be exposed to high temperatures of 500° C. or higher, and a sensor and an assembly including the sensor, using the anti-seizing agent.
2. Description of the Related Art
An anti-seizing agent is often applied to a screw portion of a metal part to prevent seizing, and the part is then used for fabrication. The metal part includes a metal shell of a gas sensor fitted to an exhaust pipe or the like of an internal combustion engine used to detect a specified gas component in a gas to be measured, and a metal shell of a temperature sensor fitted to an exhaust pipe or the like to detect the temperature of a gas to be measured. Examples of the anti-seizing agent include a paste-like anti-seizing agent comprising a lubricant base oil and a solid lubricant contained therein, and a paste-like anti-seizing agent comprising a grease obtained by semi-solidifying a lubricant base oil with a thickening agent, and a solid lubricant contained therein (for example, see Masahisa Matsunaga, et al., Handbooks of Solid Lubrication, pp. 409-416, Saiwai Shobo Co., (1978)).
Conventionally, a solid lubricant comprising a metal such as copper, aluminum or nickel, as a main component, and according to need, molybdenum disulfide or graphite combined therewith, is widely used in a paste-like anti-seizing agent that is applied to a metal part that may be exposed to high temperatures of 500° C. or higher (for example, see JP-B-8-19435).
The mechanism which allows these metals to prevent seizing is considered to be as follows. A paste-like anti-seizing agent containing the above-noted metals is applied to the requisite portion of a metal part to thereby form a uniform intervening film on the metal part. When the metal part is fabricated with another part, the intervening film is present between the metal part and the other part. As a result, when the metal part is exposed to high temperatures and then disassembled from the other part (when the metal part and the other part slide), seizing between the metal part and the other part is prevented by the lubricating action due to the softness of the metals constituting the intervening film.
3. Problems to be Solved by the Invention
However, when the metal part is fabricated with another part, the uniform intervening film formed on the metal part is localized so as to be present on only one portion in between the metal part and the other part. In such a case, a site at which the metal part and the other part are in direct contact is present, and as a result, the anti-seizing effect is not obtained.
For this reason, there is a need for an anti-seizing agent which forms an intervening film over the entire surface between a metal part and the other part even when the metal part and the other part slide, thereby exhibiting the desired anti-seizing effect.
In particular, an anti-seizing agent having sufficient seizing preventing performance for a sensor used under severe conditions at high temperature has hitherto not yet been achieved.